The reserve_mem kernel command line option may pass back a physical address, but the memory is still part of the normal memory just like using memblock_alloc() would be. This means that the physical memory returned by the reserve_mem command line option can be converted directly to virtual memory by simply using phys_to_virt(). When freeing the buffer there's no need to call vunmap() anymore as the memory allocated by reserve_mem is freed by the call to reserve_mem_release_by_name(). Because the persistent ring buffer can also be allocated via the memmap option, which *is* different than normal memory as it cannot be added back to the buddy system, it must be treated differently. It still needs to be virtually mapped to have access to it. It also can not be freed nor can it ever be memory mapped to user space. Create a new trace_array flag called TRACE_ARRAY_FL_MEMMAP which gets set if the buffer is created by the memmap option, and this will prevent the buffer from being memory mapped by user space. Also increment the ref count for memmap'ed buffers so that they can never be freed. Link: https://lore.kernel.org/all/Z-wFszhJ_9o4dc8O@kernel.org/
Unified · Split
| @@ -8492,6 +8492,10 @@ static int tracing_buffers_mmap(struct file *filp, struct vm_area_struct *vma) · 8491 unmodified lines | ||
| 8492 | 8492 | struct trace_iterator *iter = &info->iter; |
| 8493 | 8493 | int ret = 0; |
| 8494 | 8494 | |
| 8495 | + /* A memmap'ed buffer is not supported for user space mmap */ | |
| 8496 | + if (iter->tr->flags & TRACE_ARRAY_FL_MEMMAP) | |
| 8497 | + return -ENODEV; | |
| 8498 | + | |
| 8495 | 8499 | /* Currently the boot mapped buffer is not supported for mmap */ |
| 8496 | 8500 | if (iter->tr->flags & TRACE_ARRAY_FL_BOOT) |
| 8497 | 8501 | return -ENODEV; |
| @@ -9600,9 +9604,6 @@ static void free_trace_buffers(struct trace_array *tr) · 1102 unmodified lines | ||
| 9600 | 9604 | #ifdef CONFIG_TRACER_MAX_TRACE |
| 9601 | 9605 | free_trace_buffer(&tr->max_buffer); |
| 9602 | 9606 | #endif |
| 9603 | − | |
| 9604 | − if (tr->range_addr_start) | |
| 9605 | − vunmap((void *)tr->range_addr_start); | |
| 9606 | 9607 | } |
| 9607 | 9608 | |
| 9608 | 9609 | static void init_trace_flags_index(struct trace_array *tr) |
| @@ -10696,6 +10697,7 @@ static inline void do_allocate_snapshot(const char *name) { } · 1087 unmodified lines | ||
| 10696 | 10697 | __init static void enable_instances(void) |
| 10697 | 10698 | { |
| 10698 | 10699 | struct trace_array *tr; |
| 10700 | + bool memmap_area = false; | |
| 10699 | 10701 | char *curr_str; |
| 10700 | 10702 | char *name; |
| 10701 | 10703 | char *str; |
| @@ -10764,6 +10766,7 @@ __init static void enable_instances(void) · 62 unmodified lines | ||
| 10764 | 10766 | name); |
| 10765 | 10767 | continue; |
| 10766 | 10768 | } |
| 10769 | + memmap_area = true; | |
| 10767 | 10770 | } else if (tok) { |
| 10768 | 10771 | if (!reserve_mem_find_by_name(tok, &start, &size)) { |
| 10769 | 10772 | start = 0; |
| @@ -10784,7 +10787,10 @@ __init static void enable_instances(void) · 14 unmodified lines | ||
| 10784 | 10787 | continue; |
| 10785 | 10788 | } |
| 10786 | 10789 | |
| 10787 | − addr = map_pages(start, size); | |
| 10790 | + if (memmap_area) | |
| 10791 | + addr = map_pages(start, size); | |
| 10792 | + else | |
| 10793 | + addr = (unsigned long)phys_to_virt(start); | |
| 10788 | 10794 | if (addr) { |
| 10789 | 10795 | pr_info("Tracing: mapped boot instance %s at physical memory %pa of size 0x%lx\n", |
| 10790 | 10796 | name, &start, (unsigned long)size); |
| @@ -10811,10 +10817,13 @@ __init static void enable_instances(void) · 20 unmodified lines | ||
| 10811 | 10817 | update_printk_trace(tr); |
| 10812 | 10818 | |
| 10813 | 10819 | /* |
| 10814 | − * If start is set, then this is a mapped buffer, and | |
| 10815 | − * cannot be deleted by user space, so keep the reference | |
| 10816 | − * to it. | |
| 10820 | + * memmap'd buffers can not be freed. | |
| 10817 | 10821 | */ |
| 10822 | + if (memmap_area) { | |
| 10823 | + tr->flags |= TRACE_ARRAY_FL_MEMMAP; | |
| 10824 | + tr->ref++; | |
| 10825 | + } | |
| 10826 | + | |
| 10818 | 10827 | if (start) { |
| 10819 | 10828 | tr->flags |= TRACE_ARRAY_FL_BOOT | TRACE_ARRAY_FL_LAST_BOOT; |
| 10820 | 10829 | tr->range_name = no_free_ptr(rname); |
| @@ -446,6 +446,7 @@ enum { · 445 unmodified lines | ||
| 446 | 446 | TRACE_ARRAY_FL_BOOT = BIT(1), |
| 447 | 447 | TRACE_ARRAY_FL_LAST_BOOT = BIT(2), |
| 448 | 448 | TRACE_ARRAY_FL_MOD_INIT = BIT(3), |
| 449 | + TRACE_ARRAY_FL_MEMMAP = BIT(4), | |
| 449 | 450 | }; |
| 450 | 451 | |
| 451 | 452 | #ifdef CONFIG_MODULES |